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/**
* This file is part of Haketilo.
*
* Function: Main content script that runs in all frames.
*
* Copyright (C) 2021 Wojtek Kosior
* Copyright (C) 2021 jahoti
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* As additional permission under GNU GPL version 3 section 7, you
* may distribute forms of that code without the copy of the GNU
* GPL normally required by section 4, provided you include this
* license notice and, in case of non-source distribution, a URL
* through which recipients can access the Corresponding Source.
* If you modify file(s) with this exception, you may extend this
* exception to your version of the file(s), but you are not
* obligated to do so. If you do not wish to do so, delete this
* exception statement from your version.
*
* As a special exception to the GPL, any HTML file which merely
* makes function calls to this code, and for that purpose
* includes it by reference shall be deemed a separate work for
* copyright law purposes. If you modify this code, you may extend
* this exception to your version of the code, but you are not
* obligated to do so. If you do not wish to do so, delete this
* exception statement from your version.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
* I, Wojtek Kosior, thereby promise not to sue for violation of this file's
* license. Although I request that you do not make use this code in a
* proprietary program, I am not going to enforce this in court.
*/
#IMPORT content/activity_info_server.js
#FROM content/page_actions.js IMPORT handle_page_actions
#FROM common/misc.js IMPORT gen_nonce, is_privileged_url, \
csp_header_regex
#FROM common/browser.js IMPORT browser
/* CSP rule that blocks scripts according to policy's needs. */
function make_csp_rule(policy)
{
let rule = "prefetch-src 'none'; script-src-attr 'none';";
const script_src = policy.nonce !== undefined ?
`'nonce-${policy.nonce}'` : "'none'";
rule += ` script-src ${script_src}; script-src-elem ${script_src};`;
return rule;
}
document.content_loaded = document.readyState === "complete";
const wait_loaded = e => e.content_loaded ? Promise.resolve() :
new Promise(c => e.addEventListener("DOMContentLoaded", c, {once: true}));
wait_loaded(document).then(() => document.content_loaded = true);
/*
* In the case of HTML documents:
* 1. When injecting some payload we need to sanitize <meta> CSP tags before
* they reach the document.
* 2. Only <meta> tags inside <head> are considered valid by the browser and
* need to be considered.
* 3. We want to detach <html> from document, wait until its <head> completes
* loading, sanitize it and re-attach <html>.
* 4. We shall wait for anything to appear in or after <body> and take that as
* a sign <head> has finished loading.
* 5. Otherwise, getting the `DOMContentLoaded' event on the document shall also
* be a sign that <head> is fully loaded.
*/
function make_body_start_observer(DOM_element, waiting)
{
const observer = new MutationObserver(() => try_body_started(waiting));
observer.observe(DOM_element, {childList: true});
return observer;
}
function try_body_started(waiting)
{
const body = waiting.detached_html.querySelector("body");
if ((body && (body.firstChild || body.nextSibling)) ||
waiting.doc.documentElement.nextSibling) {
finish_waiting(waiting);
return true;
}
if (body && waiting.observers.length < 2)
waiting.observers.push(make_body_start_observer(body, waiting));
}
function finish_waiting(waiting)
{
if (waiting.finished)
return;
waiting.finished = true;
waiting.observers.forEach(observer => observer.disconnect());
setTimeout(waiting.callback, 0);
}
function _wait_for_head(doc, detached_html, callback)
{
const waiting = {doc, detached_html, callback, observers: []};
if (try_body_started(waiting))
return;
waiting.observers = [make_body_start_observer(detached_html, waiting)];
wait_loaded(doc).then(() => finish_waiting(waiting));
}
function wait_for_head(doc, detached_html)
{
return new Promise(cb => _wait_for_head(doc, detached_html, cb));
}
const blocked_str = "blocked";
function block_attribute(node, attr, ns=null)
{
const [hasa, geta, seta, rema] = ["has", "get", "set", "remove"]
.map(m => (n, ...args) => typeof ns === "string" ?
n[`${m}AttributeNS`](ns, ...args) : n[`${m}Attribute`](...args));
/*
* Disabling attributes by prepending `-blocked' allows them to still be
* relatively easily accessed in case they contain some useful data.
*/
const construct_name = [attr];
while (hasa(node, construct_name.join("")))
construct_name.unshift(blocked_str);
while (construct_name.length > 1) {
construct_name.shift();
const name = construct_name.join("");
seta(node, `${blocked_str}-${name}`, geta(node, name));
}
rema(node, attr);
}
/*
* Used to disable `<script>'s and `<meta>'s that have not yet been added to
* live DOM (doesn't work for those already added).
*/
function sanitize_meta(meta)
{
if (csp_header_regex.test(meta.httpEquiv) && meta.content)
block_attribute(meta, "content");
}
function sanitize_script(script)
{
script.haketilo_blocked_type = script.getAttribute("type");
script.type = "text/plain";
}
/*
* Executed after `<script>' has been connected to the DOM, when it is no longer
* eligible for being executed by the browser.
*/
function desanitize_script(script)
{
script.setAttribute("type", script.haketilo_blocked_type);
if ([null, undefined].includes(script.haketilo_blocked_type))
script.removeAttribute("type");
delete script.haketilo_blocked_type;
}
const bad_url_reg = /^data:([^,;]*ml|unknown-content-type)/i;
function sanitize_urls(element)
{
for (const attr of [...element.attributes || []]
.filter(attr => /^(href|src|data)$/i.test(attr.localName))
.filter(attr => bad_url_reg.test(attr.value)))
block_attribute(element, attr.localName, attr.namespaceURI);
}
function start_data_urls_sanitizing(doc)
{
doc.querySelectorAll("*[href], *[src], *[data]").forEach(sanitize_urls);
if (!doc.content_loaded) {
const mutation_handler = m => m.addedNodes.forEach(sanitize_urls);
const mo = new MutationObserver(ms => ms.forEach(mutation_handler));
mo.observe(doc, {childList: true, subtree: true});
wait_loaded(doc).then(() => mo.disconnect());
}
}
/*
* Normally, we block scripts with CSP. However, Mozilla does optimizations that
* cause part of the DOM to be loaded when our content scripts get to run. Thus,
* before the CSP rules we inject (for non-HTTP pages) become effective, we need
* to somehow block the execution of `<script>'s and intrinsics that were
* already there. Additionally, some browsers (IceCat 60) seem to have problems
* applying this CSP to non-inline `<scripts>' in certain scenarios.
*/
function prevent_script_execution(event)
{
if (!event.target.haketilo_payload)
event.preventDefault();
}
function mozilla_initial_block(doc)
{
doc.addEventListener("beforescriptexecute", prevent_script_execution);
for (const elem of doc.querySelectorAll("*")) {
[...elem.attributes].map(attr => attr.localName)
.filter(attr => /^on/.test(attr) && elem.wrappedJSObject[attr])
.forEach(attr => elem.wrappedJSObject[attr] = null);
}
}
/*
* Here we block all scripts of a document which might be either and
* HTMLDocument or an XMLDocument. Modifying an XML document might disrupt
* Mozilla's XML preview. This is an unfortunate thing we have to accept for
* now. XML documents *have to* be sanitized as well because they might
* contain `<script>' tags (or on* attributes) with namespace declared as
* "http://www.w3.org/1999/xhtml" or "http://www.w3.org/2000/svg" which allows
* javascript execution.
*/
async function sanitize_document(doc, policy)
{
#IF MOZILLA
/*
* Blocking of scripts that are in the DOM from the beginning. Needed for
* Mozilla.
*/
mozilla_initial_block(doc);
#ENDIF
/*
* Ensure our CSP rules are employed from the beginning. This CSP injection
* method is, when possible, going to be applied together with CSP rules
* injected using webRequest.
* Using elements namespaced as HTML makes this CSP injection also work for
* non-HTML documents.
*/
const html = new DOMParser().parseFromString(`<html><head><meta \
http-equiv="Content-Security-Policy" content="${make_csp_rule(policy)}"\
/></head><body>Loading...</body></html>`, "text/html").documentElement;
/*
* Root node gets hijacked now, to be re-attached after <head> is loaded
* and sanitized.
*/
const root = doc.documentElement;
root.replaceWith(html);
/*
* When we don't inject payload, we neither block document's CSP `<meta>'
* tags nor wait for `<head>' to be parsed.
*/
if (policy.has_payload) {
await wait_for_head(doc, root);
root.querySelectorAll("head meta")
.forEach(m => sanitize_meta(m, policy));
}
root.querySelectorAll("script").forEach(s => sanitize_script(s, policy));
html.replaceWith(root);
root.querySelectorAll("script").forEach(s => desanitize_script(s, policy));
start_data_urls_sanitizing(doc);
}
async function _disable_service_workers()
{
if (!navigator.serviceWorker)
return;
const registrations = await navigator.serviceWorker.getRegistrations();
if (registrations.length === 0)
return;
console.warn("Service Workers detected on this page! Unregistering and reloading.");
try {
await Promise.all(registrations.map(r => r.unregister()));
} finally {
location.reload();
}
/* Never actually return! */
return new Promise(() => 0);
}
/*
* Trying to use servce workers APIs might result in exceptions, for example
* when in a non-HTML document. Because of this, we wrap the function that does
* the actual work in a try {} block.
*/
async function disable_service_workers()
{
try {
await _disable_service_workers()
} catch (e) {
console.debug("Exception thrown during an attempt to detect and disable service workers.", e);
}
}
function synchronously_get_policy(url)
{
const encoded_url = encodeURIComponent(url);
const request_url = `${browser.runtime.getURL("dummy")}?url=${encoded_url}`;
try {
var xhttp = new XMLHttpRequest();
xhttp.open("GET", request_url, false);
xhttp.send();
} catch(e) {
console.error("Failure to synchronously fetch policy for url.", e);
return {allow: false};
}
const policy = /^[^?]*\?settings=(.*)$/.exec(xhttp.responseURL)[1];
return JSON.parse(decodeURIComponent(policy));
}
if (!is_privileged_url(document.URL)) {
const policy = synchronously_get_policy(document.URL);
if (!(document instanceof HTMLDocument))
delete policy.payload;
console.debug("current policy", policy);
activity_info_server.report_settings(policy);
policy.nonce = gen_nonce();
const doc_ready = Promise.all([
policy.allow ? Promise.resolve() : sanitize_document(document, policy),
policy.allow ? Promise.resolve() : disable_service_workers(),
wait_loaded(document)
]);
handle_page_actions(policy, doc_ready);
activity_info_server.start();
}
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